1. Field of the Invention
The present invention relates to printing apparatus.
More particularly, the invention relates to dot printers.
Still more specifically, the invention relates to arrangements for controlling the movements of plungers in dot printing apparatus.
2. The Prior Art
Dot printers are printing apparatuses in which reciprocable plungers or similar elements cause the application of a flowable medium to a substrate, i.e., a workpiece web, during their reciprocation. The medium, in the prior art and also hereinafter with respect to the invention, may be printing ink, adhesive, or any other flowable substance that can be applied to the substance; for convenience it will hereafter be called "printing ink".
Depending upon the spacing of adjacent plungers, or upon which ones of adjacent plungers are activated during a particular operating cycle and which ones are not activated at that time, the substrate may be printed with discrete (spaced-apart) dots (which may or may not form a pattern of e.g., lines), or the adjacent dots may merge so that the substrate is printed with e.g., a continuous coating of color (which may or may not be uni-colored).
The operation of the plungers in the prior art (i.e., the selection of which plungers are to operate and the timing of their operation) can be controlled by means of computers, punch-card controls, magnetic-tape controls and the like. The actual movement of the plungers is effected by electromagnets or pressure cylinders which cooperate with the free end of the respective plunger and which reciprocate the plunger in response to command signals issued by the computer or other control device.
While the prior-art proposals give highly satisfactory printing results, it has been found that their structural execution is rather expensive because, as explained above, each individual plunger or group of jointly moving plungers must be provided with a separate motion-imparting arrangement.